The study is designed to evaluate the safety, tolerability and efficacy of two doses of pregabalin as add-on treatment in pediatric and adult subjects with Primary Generalized Tonic-Clonic (PGTC) seizures as compared to placebo. It is hypothesized that both doses of pregabalin will demonstrated superior efficacy when compared to placebo by reducing PGTC seizure frequency and that pregabalin will be safe and well tolerated.